Gate mechanism for a data cartridge library system

ABSTRACT

Gate mechanism for a data cartridge library system including an upstanding lever arm having a laterally extending tab formed at its upper end and a generally Z-shaped member extending from its lower end, the distal end segment of the Z-shaped member forming a light-breaking flag disposed between an optical switch. The lever arm is pivotally attached proximate its lower end to a pivot member that allows the lever arm and its appendages to be rotated about orthogonal axes. An actuator is attached to the lower end of the arm so as to rotate it about one of the axes, and a spring is attached to the lower end of the lever arm to return the arm to a neutral position following its rotation about either axis. The gate mechanism is useful in blocking entry to a drive unit, limiting ejection distance of a cartridge ejected from the drive unit, and indicating when a cartridge extends out of the drive unit.

This application is a continuation-in-part of my copending applicationentitled "CAROUSEL-TYPE MAGNETIC TAPE LIBRARY SYSTEM" filed Mar. 18,1994, as U.S. Ser. No. 08/210,790 and assigned to the Assignee of thepresent application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to magnetic tape storageapparatus, and more particularly to an improved gate mechanism for usein a carousel-type magnetic tape library system to assist in thehandling of cartridges at the entries to the drive units.

2. Brief Description of the Prior Art

As pointed out in my copending applications Ser. Nos. 07/982,939;07/982,940; 07/983,345; and 07/984,294, all filed on Nov. 30, 1992 andand assigned to the assignee of the present invention, tape cartridgelibraries for use in providing relatively rapid and automatic access toa large quantity of information are in demand for backing up data onUNIX and PC networks. Although various types of systems have been madeavailable for handling 8 mm and larger-sized tapes, only recently haveauto-changer units become available for handling the smaller 4 mm-sizedcartridges. However, the presently available 4 mm systems known toApplicant are all limited to use of in-line magazines capable ofhandling twelve or fewer cartridges and do not readily accommodateoperator exchange of a single cartridge. A need therefore exists for acompact carousel library system having a lightweight apparatus that hasa simple and automatic scheme for retaining cartridges securely duringtransport and handling, and retaining them in place during motion of theapparatus, while at the same time permitting easy removal by librarymechanisms as required.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide a gate mechanismfor use in a carousel-type library system particularly suited forhandling data storage cartridges and permitting access to theinformation stored therein.

Another objective of the present invention is to provide a gatemechanism for facilitating the loading and unloading of cartridges intoand out of the drive units of a data storage system.

Briefly, a preferred embodiment of the present invention includes anupstanding lever arm having a laterally extending tab formed at itsupper end and a generally Z-shaped member extending from its lower end,the distal end segment of the Z-shaped member forming a light-breakingflag disposed between an optical switch. The lever arm is pivotallyattached proximate its lower end to a pivot member that allows the leverarm and its appendages to be rotated about orthogonal axes. An actuatoris attached to the lower end of the arm so as to rotate it about one ofthe axes, and a spring is attached to the lower end of the lever arm toreturn the arm to a neutral position following its rotation about eitheraxis. The gate mechanism is useful in blocking entry to a drive unit,limiting ejection distance of a cartridge ejected from the drive unit,and indicating when a cartridge extends out of the drive unit.

An advantage of the present invention is that it provides a simplemechanism for preventing a cartridge ejected from a drive unit frominterfering with a carousel magazine, and for indicating that acartridge has been ejected.

Another advantage of the present invention is that it provides afail-safe feature which protects against machine error during cartridgeejection from a drive unit.

These and other objects and advantages of the present invention will nodoubt become apparent to those skilled in the art after having read thefollowing detailed description of the preferred embodiment which isillustrated in the several figures of the drawing,

IN THE DRAWING

FIG. 1 is a perspective view illustrating details of a standard 4 mmhelical scan magnetic tape cartridge;

FIG. 2 is a perspective view generally illustrating the principaloperative components of a tape library system in accordance with thepresent invention;

FIG. 3 is a broken, partial cross-sectional view illustrating details ofthe access door and carousel structure of the system depicted in FIG. 2;

FIG. 4 is a plan view illustrating various details of the preferredembodiment depicted in FIG. 2 at the turntable plate level;

FIG. 5 is a partially broken plan view illustrating various details ofthe turntable, cartridge grabber and carriage subsystems of thepreferred embodiment;

FIG. 6 is a partially broken cross-section taken line 6--6 of FIG. 5;

FIGS. 6a and 6b are perspective views illustrating gate mechanism inaccordance with the present invention;

FIG. 7 is an elevational view illustrating certain details associatedwith the carriage drive components of the grabber subassembly of thepreferred embodiment;

FIG. 8 is an exploded partial plan view illustrating details of thegrabber elements depicted in FIGS. 5 and 6;

FIG. 9 is a plan view showing one side of a molded part used to form thecarousel-type magazine unit of the preferred embodiment;

FIG. 10 is a transverse cross-section depicting certain details of apreferred embodiment of a carousel-type magazine in accordance with thepresent invention;

FIG. 11 is a transverse cross-section illustrating details of acarousels-type magazine cover plate in accordance with the presentinvention;

FIG. 12 is a partially broken plan view showing details of the oppositeside of the molded part depicted in FIG. 9 together with a resilientretainer ring and cover plate in accordance with the present invention;

FIG. 13 further illustrates a roller wheel of the type depicted in FIG.12 of the drawing; and

FIGS. 14 and 15 illustrate operational sequences implemented by theillustrated preferred embodiment.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Although not necessarily limited thereto, the preferred embodiment ofthe present invention is directed to an apparatus for handlinghelical-scan 4 mm data cartridges of the type depicted in FIG. 1 of thedrawing. Access to the tape contained in the cartridge is through arotatable gate 12 on one side of the cartridge body and a sliding panel14 on the back side of the cartridge. Note that one edge 13 of the gate12 is chamfered. Advantageously, the cartridge is provided with ahandling slot 16 on the front surface, and a shoulder 18 is formed nearthe back side at the terminus of the panel slide relief 20. As will beexplained in further detail below, the slot 16 and shoulder 18 will beengaged by elements of the present invention to retain it in position,first in the external access door and then in the carousel.

Referring now to FIG. 2 of the drawing, a magnetic tape library systemis depicted generally at 22 with its outer casing removed but suggestedby the dashed lines 24. The system includes an access door assembly 25,a pivotable cartridge-receiving door 26 for facilitating the insertionand removal of cartridges 10, and a cylindrical carousel unit 28including either a removable or non-removable cylindricalcartridge-carrying magazine 27 carried by a turntable 30 rotatablymounted to a turntable support ring 33 (not shown) and plate 32 securedto the base casting 34. Turntable 30 includes a sprocket wheel 36 thatis engaged by a toothed drive belt or chain 38 connected to a steppermotor 40 affixed to plate 32. Affixed to sprocket 36 is a shutter plate42 having a plurality of notches 44 in the perimeter thereof forpurposes which will be described below. Also attached to plate 32 is anoptical turntable-indexing sensor 46, a carousel-indexing sensor 48, anda cartridge-in-carousel and cartridge-orientation sensor 50. Disposedwithin the central cavity of carousel 28 not occupied by the cartridges10 is a cartridge onloading and offloading mechanism shown generally at54. As will be described in detail below, the mechanism 54 is supportedby a base (not shown) which is rotatably mounted concentric to theturntable 30.

Disposed on the side of carousel opposite door 26 is a dual tape driveassembly including modular tape drive units 56 and 58 which are mountedto base plate 34 by a drive-support casting 60 and associated clampplate 62. A gate mechanism 63 is associated with each drive unit andpositioned between its access slot and the carousel. Also depicted andmounted to base plate 34 is a power supply and associated electronicssubsystem 64, and a cooling fan 66. Electronic access to drives 56 and58 is by ribboned cables (not shown) and suitable connectors positionedat the ports indicated by the dashed lines 68.

In FIG. 3 of the drawing, details of the access door assembly 25 and itsoperating mechanisms are depicted in brokenaway detail. Also depicted bythe dashed lines 10 is a cartridge shown in place within door 26. Theaccess door 26 and an associated lifter 70 are pivotally connected at 72to a pair of upstanding side plates 74 mounted to base 34. Also affixedto side plates 74 is an optical detector assembly 75 including a pair ofLEDs 76 (not shown) mounted on one side of door 26 opposite a pair ofphotosensors 78 aligned therewith and mounted on the near side of door26, as depicted. Pivotally secured at 80 to side plates 74 is a triplever 81 having a pair of spaced-apart arms 82 extending upwardly onopposite sides of the cartridge 10. The trip lever 81 includes a latchplate 84 extending horizontally and having an opening formed therein formatingly receiving a latch 86 affixed to door 26.

Also affixed to side plates 74 is a rubber roller 88 which is engaged bythe lower edge 90 of door 26 and serves to provide a damping resistanceto the opening of the door as well as a stop at both the open positionindicated by the dashed lines 26', and the closed position illustratedNote that the bottom-most extremities of lifter 70 and trip lever 81 areattached by a tension spring 92 that serves both to maintain latch 86 inengagement with latch plate 84, when door 26 is in its closed position,and to provide partial opening energy to lifter 70 when trip lever 81 isrotated clockwise, as depicted, allowing latch 86 to become disengagedfrom latch plate 84 and permitting door 26 to be rotated outwardly aboutpivot 72. Rotation of lifter 70 is limited. Therefore, spring 92 onlyprovides partial opening of door 26. Full rotation thereof into the openposition indicated by dashed lines 26' is manually accomplished by anoperator.

In order to ensure that a cartridge 10 is correctly oriented in door 26,a small bail-mounted roller 94 is provided on one side of the door. Thebail is spring-loaded to extend a fixed distance into the opening at thedoor. If the cartridge is correctly oriented, the roller will engage thechamfer on the front edge of the cartridge, and be moved aside to allowthe cartridge to enter until the roller drops into the slot 16,whereupon roller 94 serves to retain the cartridge in proper positionrelative to the door. Should a cartridge be incorrectly oriented, roller94 will engage an unchamfered corner and prevent its entry into thedoor. Note that this simple bail-mounted roller takes advantage of twostandard features of the cassette; namely, the chamfer 13 and slot 16,to provide both correct orientation of the cartridge, and retention of acartridge correctly oriented in the door 26 as it is rotated from anopen position to a closed position, and vice versa.

In FIG. 4, a partially broken top view of the access door assembly 25 isshown affixed to base 34 and juxtaposed to motor 40 and turntable plate32. Note that turntable plate 32 has a central opening 95 formed thereinfor receiving a support ring 96 having a hole-forming perimeterincluding three V-shaped notches 101, 102 and 103, the purpose of whichwill be described below. Also depicted in this figure is a plan view ofthe drive-support casting 60 and its associated clamp plate 62. Thefront portion of drive 56 is broken away to reveal elements of the gatemechanism 63 including an optical switch 104 for detecting the positionof a flag 106 that forms the lower end of a tortuously shaped gate lever108 that will be further illustrated and described below. The gate 108is actuated by solenoid 110 and return spring 111 that will likewise bedescribed below. Although only partially depicted, a similar gatemechanism is also associated with drive 64.

Also illustrated in FIG. 4 is the alignment of thecartridge-receiving/exiting opening 31 of access door mechanism 25 andthe cartridge-receiving openings 57 and 59 of the drives 56 and 58relative to the turntable support ring 96. As suggested by the lines 29,61 and 63, the several units are aligned such that the centerlines ofthe cartridge-receiving chambers of each unit lie along radial linesemanating from the center 33 of turntable support ring 96 and thus thecenter of turntable 30.

Depicted in FIG. 5, and in the cross-section thereof taken substantiallyalong the lines 6--6 and depicted in FIG. 6, is the turntable assembly30 and cartridge load/offload mechanism 54. As illustrated, the supportring 96 is mounted within the opening 33 in turntable plate 32 andincludes a recessed ledge 98 (FIG. 6) for receiving an annular bushing99. As suggested in FIG. 5 and more clearly shown in FIG. 6, sprocket 36is journalled to support ring 96 by an annular bearing 93. Mounted tosprocket 36 and affixed thereto by screws 116 is the turntable 30including three upstanding drive pins 118 disposed at equal intervalsaround the perimeter thereof. In the inner wall of turntable 30 aprotrusion is provided to form a stop 119. It will be appreciated thatturntable 30 is thus freely rotatable about bearing 93 or driven bymotor 40 via belt 38 and sprocket 36.

Disposed to extend downwardly through the inner opening of bushing 99and having an outwardly extending shoulder 120 for resting thereupon isa base structure 122 for the cartridge loading/offloading mechanism 54,sometimes referred to as a "grabber mechanism" or "grabber assembly".Mounted to base 122 is a carriage assembly 127 including an upstandingsupport member 124 and an outreaching support arm 125 for supporting agrabber 126 and its actuating solenoid 128. Also affixed to base 122 isa yoke 130 for supporting each end of a guide rod or shaft 132. Slidablyaffixed to guide rod 132 is the base portion 134 of support 124 ofcarriage assembly 127. Also affixed to the base portion 134 by lateraloffsets 135 (FIG. 5) is a rack 136. A carriage driving stepper motor 138having a pinion 140 affixed to its drive shaft is mounted to base 122 todrivably engage rack 136 and move the carriage along guide rod 132. Inorder to prevent the carriage from rotating about guide rod 132, aslider rail 142 having a slot 144 formed therein is also affixed to base122 for engagement by a slider pin formed by the distal end 145 of amounting bolt 146. Disposed beneath rail 142 and secured to base 134 byswitch-adjusting plate 147 is a carriage switch 148 having an actuatorarm 150 which is engaged by a projection 152 extending from the carriagebase 134.

Also shown in FIG. 6 is a grabber assembly cover 160 which rotates withthe assembly and has an opening 162 formed in its cylindrical wall forpermitting passage of carriage arm 124 and grabber 126 to engage acartridge in any of positions illustrated by the dashed lines 164 and165, the recorder position 166, and the access door position 167. Alsoshown is the turntable indexing optical switch 46.

Further detail of the gate 108, its flag 106, the optical switch 104,the actuator 110, and a pivot pin 111 is illustrated in FIGS. 6a and 6b.Gate 108 is formed of a thin metal or plastic member having anupstanding lever arm 103 with a laterally extending tab 105 at the topand a segment 107 extending from the bottom of lever arm 103 making aright-angle bend and continuing with a segment 109 parallel to theactuating axis of actuator 110 and turning again 90° to form the flag106. As depicted in both FIGS. 6a and 6b by the solid lines, arm 103 isnormally positioned in front of the drive slot 123 so that a cartridgeejected from drive 56, as indicated at 10, will engage tab 105 androtate it forwardly, as indicated by arrow 117, to a stop position, asindicated by the dashed lines 105', the position shown as 10'. With thecartridge in the position 10', optical switch 104 will be blocked by thetab in the position 106'. If subsequently actuator 110 is energized,lever arm 103 will be rotated into the position 103', illustrated inFIG. 6b by the arrow 119, clearing the drive slot 123 and allowing acartridge to be removed or loaded thereinto. When actuator 110 isde-energized, arm 103 can move back into the position 103' underinfluence of spring 113. However, if actuator 110 should be de-energizedwith a cartridge remaining in place, as indicated by the dashed lines10', as arm 103 rotates toward its rest position, as indicated by thearrow 121, the tab 105 will engage the side of cartridge 10', asindicated by the dashed lines 103', and at such time flag 106 willcontinue to block optical switch 104, as indicated at 106", therebyindicating the presence of the cartridge.

Reference is made to FIG. 7 to provide a better understanding of therelationship between stepper motor 138, pinion 140, rack 136, support124, carriage base 134, guide rod 132, grabber actuator solenoid 128,guide rail 142, guide pin 145, and switch 148. Also illustrated is thecylindrical lower portion of base 122 and the shoulder 120 which slidesupon the bushing 99 as depicted in FIG. 6.

Referring now to FIG. 8 of the drawing, and additionally to FIGS. 5 and6, details of the grabber mechanism per se will be disclosed. In FIGS. 5and 6, it will be observed that an internally threaded shaft 170 isaffixed to the armature plate 171 of actuator solenoid 128, and hasthreaded into the end thereof a threaded stud 172 (part of 174) with alock nut 173 provided thereon for locking the stud relative to shaft170. Integral with the shank of stud 172 is a puller bar 174 having alongitudinal slot 176 (FIG. 6) formed therein, and a spring 178 disposedwithin slot 176. Spring 178 has one end pinned to bar 174 at 180 and theother end pinned to carriage arm 125 by a pin 182 that extends upwardlythrough a vertically oriented slot 184 (FIG. 8). Note that the functionof spring 178 is to apply a resilient biasing force tending to pull rod174 away from actuator 128, opening the grabber fingers.

Extending through the end portion of the carriage arm 125 on either sidethereof are pins 186, the two pins serving as pivots for a pair ofcartridge-grabbing fingers 188. As best shown in FIG. 8, each of thefingers have a radially extending tooth 190 provided thereon forengaging a corresponding notch 192 in the end portion of puller bar 174.A plastic nose plate 194 cooperates with the upper surface 196 ofcarriage arm 125 and the fingers 188 to form a capture for the distalend of puller bar 174 and provide a nose 191 for engaging a cartridge10.

It will be appreciated that by rotatably adjusting the shaft 172 andlocking it in place with nut 173, the rest position of puller bar 174,and thus the spread of fingers 188 in the illustrated gripping position,can be selected. Any spreading of the fingers 188 will tend to pullpuller bar 174 away from actuator 128 but will be resisted by spring178. Accordingly, anything wider than the illustrated distance betweenthe tips of fingers 188 will be gripped with a force determined byspring 178. Upon actuation of solenoid 128, bar 174 will be moved towardsolenoid 128 causing fingers 188 to be rotated inwardly to theillustrated cartridge gripping position.

Referring now collectively to FIGS. 9, 10, 11 and 12, the variouscomponent parts of a carousel magazine unit are illustrated. Thecarousel magazine unit is comprised of two identical molded parts 200stacked face to face and joined at the line 202, as depicted in FIG. 10.Each part is comprised of a base portion 204 having a circular aperture206 formed concentric therewith and including a plurality of dividerelements 208 defining cartridge-receiving slots 210 and oval-shapedreceptacles 212 for receiving the drive pins 118 depicted in FIGS. 5 and6. In addition, five of the dividers include stand-off elements 214(FIG. 10) having half-round tabs 216 and cavities 217 formed at theirdistal ends which serve as mating keys when two of the units 200 aremated together as depicted in FIG. 10. One of the tab/slot forming ends219 of the standoffs 214 is reversed, as compared to the others, so asto insure that the two parts 200 can only be mated in a particularorientation. As a consequence, the top part's slot 213 will have aparticular positional relationship to that of the bottom part. Note thatthe stand-offs 214 are bored and counterbored to receive a bolt 247 forlocking the two parts together. Each part likewise includes a pluralityof small slots 218 each positioned in alignment with a side portion of aslot 210 (FIG. 9) and having a vertical transverse slot 220 entering theopposite side as depicted in FIG. 12. Disposed within each of the slots218 is a small pinwheel-shaped object, such as that depicted in FIG. 13,comprised of a small metal or molded plastic wheel 222 with integralshafts 224. The wheels 222 fit into slots 218, and the shafts 224 fit inslots 220.

A metal retainer plate 226, having a plurality of inwardly directedspring fingers 228, aperture tabs 230 and outwardly extending tabs 232,is positioned over the annular depressed region 233 formed on theopposite side of the upper part 200, and the tabs 230 are forced overthe standing studs 234 such that the apertures in the tabs frictionallyengage the studs and the tabs 232 interfere with the shoulder formingthe depression 233, thereby biasing the fingers 228 flat against thesurface of 233. The spring fingers thus engage the tops of the wheels222 forcing them downwardly so as to protrude into thecartridge-receiving slots 210. Retaining engagement of a wheel 222 witha cartridge is depicted in FIG. 3.

In FIG. 11, a carousel cover and lifting handle plate 240 is depictedshowing three of five short downwardly extending legs 242 and webs 243for engagement within the frusto-conically shaped recesses 244 formed inthe outer side of the parts 200, depicted in FIGS. 10 and 12. In orderto secure the top to the carousel parts 200, rough threads can be formedin a bore 246 extending into the bottom side of legs 242 for engagementby a bolt extended through the bores 248 formed in the stand-offs 214.Alternatively, as depicted in FIG. 3, a bored insert or sleeve 250 couldbe positioned in the bores 248 of the upper parts 200 for threadablyreceiving screws 247 extending up through the bottom-most parts. The top240 could be likewise secured thereto by threading a screw 252 into thesleeve 250.

Having thus described the component parts of the library system, thefollowing summary is offered to provide an understanding of how theseveral parts interact.

Referring again to FIG. 2 of the drawing, a carousel 28 is providedwhich is less than 8 inches in diameter and holds 25 4 mm cartridges. Aspreviously described and depicted in FIGS. 9-12, identicalinjection-molded plastic parts 200 are used for both the top half andthe bottom half of the carousel body. 0n the facing surfaces of the twoparts, as indicated in FIG. 9, features are provided which locate andguide the cartridges. Twenty of the features 214 are of minimum heightwhile five of the features include stand-offs that extend to themidplane of the magazine. Projections from these longer features, orstand-offs, locate and orient the two halves.

As indicated in FIG. 9, a notch 213 extends radially inwardly throughone of the minimum-height features. The notch 213 in the bottom part issensed by the angled LED and optical sensor 48 (FIG. 2) to establish acarousel index. The corresponding notch 213 in the top half of themagazine is used to orient the top cover 240. More specifically, a tab241 in cover 240 mates with the notch 213, as depicted in FIG. 12. Aspreviously indicated, due to the orientation of the tab 216 and cavity217 in the standoff 219, the magazine can only be assembled in one way.This insures that the index numbers 241 (FIG. 12) in top 240 have apredetermined relationship to the slot 213 in the bottom part 200. Theslotted holes 245, best shown in FIG. 12 but also designated as 212 inthe lower part 200 shown in FIG. 10, have frusto-conical lead-ins 244,which in the case of the lower part serve to facilitate engagement withthe three pins 118, shown in FIGS. 5 and 6.

The magazine 28 can thus be easily installed in the library unit withoutregard to angular orientation. The weight of the magazine holds it inengagement with the turntable flange, as partially depicted in FIG. 3 ofthe drawing. The pins 118 and slotted holes 245 also accurately centerthe magazine on the turntable 30 and transmit torque from the turntableto the magazine.

As variously depicted in FIGS. 3, 10 and 12, twenty-five small rollers222 with integral axis 224, as depicted in FIG. 13, fit in narrowelongated holes and slots 218 and 220 (FIG. 12) molded into the carouselparts 200. However, the rollers are only installed in the top part. Theself-retaining one-piece spring 226, shown in FIG. 12, has twenty-fivefingers 228 which engage and hold the rollers 222 in place and provideindependent spring action. As depicted in FIGS. 3 and 10, part of eachroller 222 protrudes into the slot to be occupied by a cartridge. Theprotruding part of the roller fits into a relieved portion of thecartridge and thereby holds the cartridge securely within the magazineslot. The injected-molded plastic top cover 240 covers the spring 226and rollers 222 and includes a handle 243 that bridges the centralopening of the magazine. Cartridge identification numbers are moldedinto the cover 240, as illustrated, so as to identify each of thetwenty-five cartridge slots.

As depicted in FIGS. 3 and 10, the magazine halves and top are all heldtogether with five screws 247 which are installed from the bottom.

As best depicted in FIGS. 5 and 6, a flanged cast-aluminum turntable 30rotates on the outer diameter of a thin cross-section X-type ballbearing 93, and a six-inch pitch diameter sprocket 36 is sandwichedbetween the turntable and a notched shutter plate 42. The sprocket 36fits against the outer race of the bearing, and a stepper motor 40(FIGS. 2 and 4) drives the turntable 30 via a positive-drive,no-backlash belt 38 and sprocket wheel 39. The sprocket ratio isselected so that

    RATIO=(no. cartridges)×(4n/(steps/rev))

where n is an integer. As illustrated in FIG. 2, shutter plate 42 hasone large notch 43 and twenty-four smaller notches 42. The opticalswitch 46 fits around the shutter plate to sense passage of the notches42 and 43. The large notch 43 and a specific phase of motor 40 establishthe turntable index. The control system calculates the offset betweenthe turntable index and the carousel index during initialization. Thesmall notches verify turntable rotation. The angular position ofturntable 30 is factory-adjusted by rotating the motor 40. The innerrace of bearing 96 is fixed to a cylindrical aluminum support member 96which has a pilot diameter 100, as depicted in FIG. 4, and fits within ahole in the sheet metal turntable mounting plate 32. The mounting plate32 has a datum hole and slot (not shown) that fit pins (not shown)provided in the base plate 34. The turntable assembly including thedrive motor 40 is a field-replaceable unit (FRU).

The large cylindrical plastic bushing 99 (FIGS. 4 and 6) fits in arecess on top of the support 96. As depicted in FIGS. 4 and 6, thesurface 100 forming an edge to the support surface 99 is irregular andis provided with three V-shaped notches 101-103. Two of the notches, 102and 103, are respectively aligned with the tape drives 56 and 58. Thethird notch, 101, is aligned with the access door 26. As depicted inFIG. 6, the cast-aluminum grabber base 122 has a flange 120 and acylindrical projection extending downwardly. The grabber base 122 fitsin and rests on the plastic bushing 99. Bushing 99 allows the grabberbase to rotate independent of, but concentric with, the turntable 30with little friction or wear. A spring-loaded plunger 105 (FIG. 6)protrudes in a radial direction near the bottom of the grabber base andwill detent into one of the three notches in the support 96, therebyaligning the grabber base with the drives or the access door. The top ofthe grabber base has two arms 130 which extend from the base and holdthe carriage guide rod 132. The arms and guide rod are positioned belowthe carousel mounting surface 31 of the turntable 30. Note that, asdepicted in FIG. 5, one end 133 of guide rod 132 extends slightly beyondthe limits of the arm 130. When the exposed end of the guide rodcontacts the inward facing protrusion 119 on the turntable 30, theturntable can rotate the grabber base 122 to one of the three detentedgrabber positions. After rotating the grabber base, the turntable 30 isthen free to rotate any of the cartridges into alignment with either theaccess door or one of the drives.

Only one motor, i.e. motor 40 (FIGS. 2 and 4), is required since theturntable drive motor does double duty. More specifically, the grabberbase 122 is prevented from rotating more than necessary (182.4°) by twopins 135 and 137 protruding from the top of the support 96, and a radialprotrusion 139 from the grabber base flange 122. The grabber base 122 isheld down by gravity. However, it cannot be removed unless the plunger105 and an opposing pin 107 are aligned with notches (not shown) formedin the bushing 99. The grabber assembly 54 is also a field-replaceableunit (FRU). Advantageously, the turntable/grabber base assembly is verycompact, i.e. only slightly over an inch thick. As an alternative to theembodiment shown, the turntable, sprocket, pins and bearing could becombined in one injection-molded part.

The carriage including arm 124 is a cast-aluminum part having bronzebushings 131 (FIG. 6) and, as previously indicated, is driven along theguide rod or shaft 132 by the small stepper motor 138, a pinion 140attached to the motor shaft, and a rack 136 forming a part of thecarriage. The motor and pinion are selected to provide sufficient forceto load a cartridge into the tape drives 56 and 58 (FIG. 4). Aspreviously described, carriage rotation is prevented by the pin 145sliding in a slot 144 (FIGS. 5 and 7). The lower part of the carriagehas a projection. 152 (FIG. 5) that contacts the switch arm 150 ofswitch 148 when the carriage is in the retracted position. The retractedposition of the switch is factory-adjusted,

The carriage supports a low-profile solenoid 128, the center of which isin line with the center of cartridges disposed in the carousel. Thesolenoid plunger is adjustably connected to the rectangular puller bar174 by means of the threaded assembly 170, 172, 173 (FIG. 6). Puller bar174 has two vertical grooves or notches 192 (FIG. 8) provided therein atthe end opposite the solenoid. The two small rotatable grabber fingers188 are pivotally secured to carriage arm 125 by pivot pins 186 and haveprotrusions 190 that fit in the grooves 192. When the puller bar ismoved a small distance (approximately 0.029 inch) by solenoid 128, thegrabber fingers rotate towards each other in a pincer motion. Whensolenoid 128 is not energized, the tips of the fingers 188 are heldnormally open by the small spring 178 (FIGS. 6 and 8) attached to thepuller bar and carriage arm 125.

The spacing of the closed tips of the grabber fingers 188 is normallyadjusted to be approximately 0.05 inch less than the thickness of acartridge to be engaged. The maximum separation of the closed grabberfingers is selected so that the overall width thereof is less than theminimum spacing between cartridges as they are placed in the carousel.Therefore, when the solenoid 128 is energized, the closed ends of thegrabber fingertips can be used to push a cartridge out of the carouseland into a tape drive or the access door. With the grabber fingertipsopen they easily fit around a cartridge. When the grabber is open andsolenoid 128 is energized, the grabber fingertips can firmly grip acartridge so that it can be drawn into the carousel from the tape driveor the access door. As illustrated in FIG. 8, the grabber fingers andpuller bar are captured by plastic guides 191 designed to form a "nose"for contacting a cartridge when the cartridge is in a grabbableposition.

The carriage, solenoid and motor forming the mechanism 54 all fit withinthe central opening of the carousel magazine. The rack and bushingportion of the mechanism are positioned below the carousel. Althoughprototype grabbers were made by stacking photo-etched parts, it isanticipated that production parts will be fabricated of sintered steel.The prototype carriage is designed as a machined aluminum casting withbushings, but the rack 136 is made of steel. Alternatively, the carriagerack and bushings could be combined in a single injection-molded plasticpart.

The downwardly pivoting access door 26 provided at the front of the unithas an opening axis that is perpendicular to the axis of the carousel.The door is made of injection-molded plastic and, when open, will accepta correctly oriented cartridge. As previously described, the cartridgeshave a small chamfer on one of the leading edges, and, if orientedcorrectly, the chamfer will move the small spring-loaded roller 94(FIGS. 3 and 6) out of the way. However, once the cartridge is loaded,the roller 94 assists in holding the cartridge in the door. The door isclosed by hand and has a front surface that, when the door is closed, isflush with the front panel of the unit. The two LEDs 76 (FIGS. 3 and 4)and two sensors 78 monitor door open/close and cartridge present. Thelatch 86 engages trip lever 82 when the door is fully closed. The triplever 82 may be rotated about an axis 80 parallel to the axis 72 of thedoor 26 when engaged by the tips of the grabber fingers, therebyallowing the spring-loaded lifter 70 to apply a limited rotation torqueto open the door. The lifter rotates about the same axis as the door.The same spring, i.e. spring 92, is used to apply force to the lifterand the trip lever.

The upwardly extending legs forming the upper portion of the trip lever82 are spread far enough to fit around a cartridge. Moreover, thespacing between the legs is made wide enough for the grabber fingers topass through when closed but narrow enough to insure that they areengaged by the ends of the grabber fingers when the grabber solenoid isde-energized. To pull a cartridge out of the door and into the carousel,the grabber is extended with its fingers closed until the tips are pastthe legs of the trip lever, The solenoid 128 is then de-energizedallowing the spring 178 (FIG. 6) to expand the grabber fingers to thegrab position. Solenoid 128 is then again energized and the cartridge isengaged by the fingers and withdrawn into the carousel by energizingstepper motor 138.

To offload a cartridge from the carousel to the door, the closedfingertips are caused to engage the cartridge exterior and push thecartridge out of the carousel and through the legs of the trip lever 82into the door 26. To then open the door, the carriage is withdrawn farenough for the closed grabber fingertips to clear the trip lever 82, andsolenoid 128 is de-energized, allowing the tips to open. The carriage isthen moved outwardly far enough to engage and rotate the trip levertoward the door to release the latch and allow the door to be rotatedoutwardly under the influence of spring 92 and lifter 70. The doorinitially rotates about 20° under action of the lifter with the rubberroller 88 (FIG. 3) contacting cam surface 90 in the bottom of the doorand gently stopping the partially opened door. The upper corner of thedoor at this point protrudes far enough from the front of the unit foran operator to grip it and pull it open. The rubber roller/cam preventsthe door from falling open and provides soft stops when the door isopened and when it is closed. The door assembly is a field-replaceableunit (FRU) and is installed without adjustment.

The library unit is designed to be used with unmodified tape drivesavailable from several vendors. 4 mm tape drives normally are auto-loadand auto-eject (similar to most VCRs). To load, the cartridges areinserted in a slot in the drive and pushed partway into the driveagainst a spring. The cartridges are automatically unloaded but are notejected a fixed distance. This is to say that the ejected extension ofthe cartridge out of the drive varies from drive to drive. In accordancewith the present invention, the gate mechanism (best shown in FIGS. 6aand 6b) is used to:

(1) stop the cartridge 10 at a controlled location 10' clear of themagazine exterior;

(2) indicate that a cartridge has been ejected and is in the position10' ready to be pulled into the carousel magazine; and

(3) check that the cartridge path is clear before rotating the carousel.

As depicted, the lever arm 109 extends up from the pivot point 111 belowthe carousel to just below the midpoint of a cartridge 10. The lever canrotate about an axis a₁ parallel to the cartridge motion and also haslimited rotation about an axis a₂ normal to the cartridge motion. Asingle, angled spring 113 below the pivot 111 rotates the top 105 of thelever arm 103 about the pivot 111 both toward the tape drive 56 andtoward the drive slot 123 in the drive. The top of the lever arm has aprojection or tab 105 which protrudes in front of the cartridge slot.The small solenoid 110 connected to the lever arm below the pivot 111has an actuating axis a₃ normal to the direction of cartridge motion andparallel to axis a₂. The flag portion 106 of gate 108 extends from thelower part of the lever arm 103 below the pivot 111 into a positionbetween the legs of the U-shaped optical switch 104. The flag portion106 is designed so that rotation about either of the two orthogonal axesa₁ and a₂ defined by pin 111 and actuator 110 will block the opticalswitch. The optical switch is normally open (not blocked), as depictedby the solid lines in FIGS. 6a and 6b.

When solenoid 110 is energized, it causes the top 105 of lever arm 103to rotate away from the drive slot 123, as indicated by arrow 119 inFIG. 6b. This rotation causes the flag end 106 to move upwardly andblock the optical switch 104. With the cartridge slot clear, a cartridge10 can be pushed from the carousel magazine into the drive 56. After thecartridge is loaded, the solenoid 110 is de-energized allowing spring113 to position the upper end 105 in front of the drive slot 123. Whenthe drive ejects the cartridge, the cartridge 10 contacts the projection105, and since the cartridge unload spring (not shown) in the drive isstronger than the lever spring 113, the cartridge causes lever arm 103to rotate rightwardly against a stop 115 at the bottom end of the lever.Lever rotation caused by the unloaded cartridge 10' also causes the flagend 106 to block the optical switch 104 (FIG. 6a). With the cartridgenow in a known position, the grabber carriage is moved out through thecarousel and extended until the grabber nose 191 (FIG. 8) contacts thecartridge and partially re-inserts it into the drive. At this point, thecartridge is no longer pressing against the lever arm 103, and the gatesolenoid 110 can be energized to move the gate out of its blockingposition. After the gate is clear of the cartridge, actuator 128 (FIG.6) is energized and the cartridge is engaged by the grabber fingers andis withdrawn out of the drive and into a carousel slot, and the solenoid110 is de-energized, allowing the lever arm 103 and tab 105 to move backinto position in front of the drive unit. If the cartridge was notsuccessfully pulled into the carousel, the tab 105 will rest against thecartridge, as illustrated at 103" in FIG. 6band not return to its normalposition. In this position, the optical switch 104 is blocked,indicating that a retry is required. The cartridge gate mechanism is afield-replaceable unit (FRU) and requires no adjustment.

A typical operational sequence is illustrated by the timing diagramshown in FIGS. 14 and 15. However, many variations to the illustratedsequence can be orchestrated by the system controller electronics andassociated software. The numbers indicated in FIGS. 14 and 15 aredefined by the following list:

(1) Grabber aligned with Drive B. Turntable in home position.

(2) Grabber aligned with Drive B. Slot XX aligned with drive B.

(3) Target cartridge aligned with drive B.

(4) Target cartridge should be in drive B.

(5) If CIP sensor stays on, initiate retry procedure.

(6) If STEPS OUT STEPS IN, initiate retry procedure.

(7) Drive ejects cartridge.

(8) Grabber aligned with drive A.

(9) Grabber aligned with door.

(10) Target cartridge aligned with door.

(11) Operator closes door.

(12) Target cartridge in door.

Although the present invention has been described above in terms of aspecific embodiment, it is anticipated that alterations andmodifications, and perhaps other uses thereof will become apparent tothose skilled in the art. For example, the illustrated unit and itsseveral component parts may be modified to load VHS video cassettes,audio cassettes, or other media packages into corresponding drives. Itis therefore intended that the following claims be interpreted ascovering all such alterations and modifications as fall within the truespirit and scope of the invention.

What is claimed is:
 1. A gate mechanism for use in association with adrive unit used to record/play back information contained in a cartridgeinsertable thereinto, comprising:pivot means; spring means; actuatormeans; optical switch means having an interruptable light path andoperative to generate an electrical signal when said light path isinterrupted; and means forming an elongated upstanding lever arm havinga flag arm extending therefrom, said lever arm being pivotally attachedto said pivot means and rotatable about orthogonal first and second axespassing through said pivot means, said lever arm being normally held ina first position by said spring means, said lever arm being rotatableabout said first axis by said actuator means to a second position inwhich said flag arm is caused to interrupt said light path, said leverarm being engageable by a cartridge ejected from the drive unit androtatable about said second axis to a third position in which said flagarm is caused to interrupt said light path.
 2. A gate mechanism asrecited in claim 1, wherein said flag arm is generally Z-shaped andhas:a first component affixed to the lower end of said lever arm andextending away from said lever arm and parallel to said first axis; asecond component affixed to said first component and extending parallelto said second axis; and a third component affixed to said secondcomponent and extending parallel to said first axis, said thirdcomponent forming a flag for interrupting said light path when saidlever arm is in said second position and said third position.
 3. A gatemechanism as recited in claim 2 wherein said spring means is a tensionspring attached to said lever arm and is operable to return said leverarm from said second position and said third position to said firstposition.
 4. A gate mechanism as recited in claim 3 wherein said leverarm includes a tab extending laterally relative to the length of saidlever arm, said tab being engageable by a cartridge ejected from saiddrive unit when said lever arm is in said first position.
 5. A gatemechanism as recited in claim 4, and further including stop means forlimiting the extent to which said lever arm can be rotated about saidfirst and second axes, said stop means thereby defining said second andthird positions.
 6. A gate mechanism as recited in claim 1 wherein saidspring means is a tension spring attached to said lever arm and isoperable to return said lever arm from said second position and saidthird position to said first position.
 7. A gate mechanism as recited inclaim 1 wherein said lever arm includes a tab extending laterallyrelative to the length of said lever arm, said tab being engageable by acartridge ejected from said drive unit when said lever arm is in saidfirst position.
 8. A gate mechanism as recited in claim 1, and furtherincluding stop means for limiting the extent to which said lever arm canbe rotated about said first and second axes, said stop means therebydefining said second and third positions.
 9. A gate mechanism as recitedin claim 1 wherein if in returning from said second position to saidfirst position said lever arm engages a cartridge, said flag arm will becaused to interrupt said light path and cause a signal to be generated.